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Phaseolus vulgaris
Fabaceae
The three bean records in this database, green bean, bush bean and fava (broad bean), all sit in the same narrow soil window: pH 6.0 to 7.0, well-drained, and neither waterlogged nor droughted through pod fill. That window is not a preference, it is a biological constraint. Rhizobium nodules (the reason a bean feeds itself) stop fixing atmospheric nitrogen below about pH 6.0, and fava shows aluminium and manganese toxicity on acid ground before the common beans do. Lime to 6.0-6.5 if a test comes back under 6.0, then re-test: the correction takes months, not weeks.
| Bean | Sow depth | Spacing | Soil temperature |
|---|---|---|---|
| Green bean | 1–1.5 in (2.5–4 cm) | 3–4 in in-row, 18–24 in apart | 60°F (16°C) or warmer |
| Bush bean | 1–1.5 in (2.5–4 cm) | 3–4 in in-row, 18–24 in apart | 60°F (16°C) or warmer |
| Fava bean | 1–2 in (2.5–5 cm) | 4–6 in in-row, 24 in apart | 40–50°F (5–10°C) |
Depth. Sow bean seed at about three times its own thickness and no deeper: 1 to 1.5 inches for green and bush bean, 1 to 2 inches for the larger fava seed. Sowing shallow is the safer error. Common bean will not germinate in soil still below 60°F (16°C) (seed sits and rots instead of swelling) while fava is the opposite and goes in four to six weeks before the last frost, which is why it also works as an autumn sowing. Neither wants a presoak: hydrate the bed, not the seed.
Spacing. Bush types are determinate and stop growing on their own, so 3 to 4 inches within the row and 18 to 24 inches between rows gives a canopy that closes without crowding; thinned stands dry out and crack their pods. Fava is taller and stiffer, so it takes 4 to 6 inches in the row with 24 inches between rows, and it benefits from a stake on exposed ground. Pole types are a different question: they need the trellis before the seed goes in.
After sowing. About an inch of water a week, held evenly through flowering and pod set: a dry week at first bloom drops the flower set, and a waterlogged week at harvest splits the pods. Inoculate seed if the bed has not grown a legume in the last four years, keep fresh manure out of the hole (it delays nodulation) and feed phosphorus and potash from a soil test rather than by habit. Full sun for all three. For the pH side of that, start from the soil pH by crop reference table and work out the rate with the lime requirement calculator.